Vehicle air bags are provided to protect occupants of vehicles during collisions. To cause the air bags to inflate, deceleration sensors have been provided that generate signals representative of sudden vehicle deceleration. When the sensed deceleration exceeds a threshold, a collision signal is generated. This signal is sent to an air bag actuator to cause the actuator to rapidly inflate the air bag.
Existing deceleration sensors use electric power which must be carried to the sensors to actuate them. To prevent electromagnetic interference (EMI) from other components of the vehicle from unduly affecting the performance of the air bag inflation system, the electric wires that carry the signals to the sensors must be shielded, adding to the cost and complexity of the system. Additionally, the use of electric deceleration sensors frequently entails using gold contacts, which can be expensive. Moreover, steps must be taken to ensure that power is not lost to the sensors during a collision. In those accidents in which the first components of the vehicle to be seriously damaged include the electrical cable that activates the air bag, there is a significant risk that the air bags will not deploy, thus depriving the occupants of their vehicle of their protection.
The present invention recognizes that the above-stated drawbacks are inherent with deceleration sensors that output electric signals representative of a vehicle's deceleration. Fortunately, the present invention understands that an effective, simple, low-cost deceleration sensor can be provided that does not require or consume electric power.